A TFT-LCD has the advantages of portability, low power consumption, and low radiation, and has been widely used in various portable information products such as notebooks, personal digital assistants (PDAs), video cameras and the like. Furthermore, the TFT-LCD is considered by many to have the potential to completely replace CRT (cathode ray tube) monitors and televisions.
A TFT-LCD generally includes a color filter substrate, a TFT array substrate, and a liquid crystal layer sandwiched between the two substrates. When a TFT-LCD works, an electric field is applied to the liquid crystal molecules of the liquid crystal layer. At least some of the liquid crystal molecules change their orientations, whereby the liquid crystal layer provides anisotropic transmittance of light therethrough. Thus the amount of the light penetrating the color filter substrate is adjusted by controlling the strength of the electric field. In this way, desired pixel colors are obtained at the color filter substrate, and the arrayed combination of the pixel colors provides an image viewed on a display screen of the TFT-LCD.
Normally, the TFT array substrate includes a plurality of gate lines that are parallel to each other and extend along a first direction, and a plurality of data lines that are parallel to each other and extend along a second direction orthogonal to the first direction. The smallest rectangular area formed by any two adjacent gate lines together with any two adjacent data lines defines a pixel unit thereat. Each pixel unit includes a TFT which functions as a switching element, and a pixel electrode connected to the TFT.
As described above, the TFT array substrate has wiring patterns such as the gate lines and data lines, which supply signals to drive the pixel electrodes. However, the wiring patterns are liable to easily disconnect during heat treatment or etching processes when the TFT array substrate is being fabricated. That is, open or short circuits are liable to occur in the wiring patterns. The size and the resolution of certain contemporary TFT-LCD devices continue to increase with each new product release. Thus, a modern TFT array substrate may be required to have large numbers of data lines and gate lines each with a very narrow line width. The difficulties in fabricating such kind of TFT array substrate are also increased, with a greater possibility of broken wiring patterns. Accordingly, various repairing methods have been devised, whereby the corresponding TFT-LCD can operate correctly despite having sustained broken wiring.
FIG. 5 is a schematic, top plan view illustrating aspects of a typical method of repairing disconnected gate lines. An LCD (not shown) includes a TFT array substrate 10. The TFT array substrate 10 includes a display region 20. The display region 20 has a plurality of horizontally extended gate lines 16, and a plurality of vertically extended data lines 12, thereby forming an array of rectangular pixel regions (not labeled). The TFT array substrate 10 also includes a plurality of repair lines 22, 23, 24, which are formed to cross the data lines 12 and the gate lines 16 outside the display region 20.
When a broken point “A” occurs at the gate line 16, laser fusing or other known techniques can be used to connect points 26A and 26B, which are located where the broken gate line 16 meets the repair line 24. Then, the repair line 24 is cut off at positions 28A and 28B. Thus, the broken gate line 16 is connected through the repair line 24.
However, a capacitor exists between the repair line 24 and the repaired gate line 16. When signals transmit through the repair line 24, the signals are liable to be distorted at either or both of the crossing points 26A and 26B. In addition, if the number of gate lines 16 is very large, there may be numerous repaired gate lines 16 and numerous crossing points through which signals are passing. The relatively large number of capacitors means that the overall signal quality in the TFT array substrate 10 may be unsatisfactory. Furthermore, depending on the location of the broken data line 16, a large delay may occur due to the resistance and capacitance of the repair line 24 between opposite ends of the broken gate line 16. The increased delay may be unacceptable for large, high-resolution TFT-LCDs. Moreover, one single gate line 16 is generally repaired using one single repair line 24, and the number of repair lines 22, 23, 24 is limited due to the size of the display region 20.
What is needed, therefore, is a method of repairing broken gate lines without using repair lines, in order to overcome the above-described deficiencies.